In order to measure the state of charge of primary batteries, it is usually necessary to measure the current or voltage of the battery under test. The testing of current and voltage is usually performed with external test equipment, such as voltmeters and battery testers. The cost of the associated test equipment or testers varies widely. There are expensive digital multimeters that will measure both voltage and current as well as inexpensive units that utilize simple resistor calibrated galvometers. There is also a heat sensing material that changes color when the material is heated up by an electrical conductor that is placed across the battery terminals. In all cases of primary battery state of charge detection, it has been necessary to place the battery either in or near the tester and then activate the test. In some units, the placing of the battery in the tester itself causes contact to be made which initiates the test. In other cases, external leads from the tester are brought to the battery terminals to initiate the test. In some cases, the state of charge reading is monitored continuously by the test instrument but in most cases is done briefly in order to provide a quick sampling of state of charge.
The principal problem with all of these methods is that an external tester of some kind must be used to measure the state of charge of primary batteries. The battery alone will not render any state of charge information to the user.
Accordingly, it is an object of the invention to provide state of charge information of a primary battery by installing an indicator on the battery.
It is a further object of the invention to provide state of charge information of a primary battery by installing an indicator that is always monitoring the state of charge continuously without a need for a switch or activator.
It is a further object of the invention to provide a state of charge indicator that is installed as a permanent part of a battery without causing any drain or reduction in performance of the battery.
It is a further object of the invention to provide a state of charge indicator that is installed as a permanent part of the battery without changing any of the outside dimensions of the battery.
It is a further object of the invention to provide a state of charge indicator that is installed as a permanent part of a battery without changing the standard contact formats of the battery.
It is a further object of the invention to provide a state of charge indicator that is installed as a permanent part of a battery with an indicator display that is easy to read and understand.